Preclinical investigation of PI3K inhibition and immune checkpoint blockade combination therapy for treatment of Merkel cell carcinoma using humanized mouse models

默克尔细胞癌（MCC）是一种侵袭性皮肤癌，发病率翻了两番， 晚期疾病的年生存率低于18%。MCC不成比例地主要影响 65岁以上的白人男性在我们的退伍军人中有很好的代表性，特别是那些 部署到高紫外线指数的热带和亚热带地区，由于其他生存 优先事项因此，MCC对VA医疗保健系统的影响越来越大。目前，没有食品和药物 美国食品药品监督管理局（FDA）批准的MCC靶向治疗。最近，免疫疗法如派姆单抗 和avelumab已被FDA批准用于晚期MCC;然而，很大一部分患者仍然 死于疾病因此，临床上迫切需要新的治疗策略， 免疫治疗失败或不适合免疫治疗。PI 3 K通路的异常扩增和突变已被发现， 在高达80%的MCC中检测到，使其成为有吸引力的治疗靶点。这是我们的临床支持。 成功地用第一个FDA批准的PI 3 K-β抑制剂idelalisib治疗IV期MCC患者， 完全临床反应。此外，我们的初步研究表明，copanlisib，第二个FDA 批准的PI 3 K抑制剂，主要针对PI 3 K-α/β亚型，发挥最有效的抗肿瘤作用 对MCC的影响。与该提议相关的是，已报道PI 3 K抑制可增强癌症 免疫疗法因此，有很强的理由来开发新的组合免疫疗法， 治疗，以提高MCC的治疗反应和疗效。缺乏同基因/基因工程动物 模型阻碍了MCC的临床前研究。值得注意的是，在我们的初步研究中， 在小鼠中建立了强大的、临床相关的MCC异种移植肿瘤模型系统， 免疫系统我们假设copanlisib对PI 3 K的抑制作用和pembrolizumab对PD-1的阻断作用， 通过抑制MCC细胞增殖和存活协同减弱MCC肿瘤生长 免疫细胞的肿瘤浸润及其抗肿瘤活性。此外，我们还优化了创新 单细胞RNA测序（scRNA-seq）方法来检查肿瘤异质性和转录组谱， 人MCC细胞。因此，我们有能力实现以下具体目标：（目标1）审查 copanlisib和pembrolizumab治疗MCC的治疗功效并确定其潜在机制 人源化小鼠异种移植肿瘤生长，以及（目的2）鉴定MCC的细胞和分子机制 肿瘤-免疫相互作用和抗肿瘤免疫应答copanlisib和pembrolizumab治疗。 使用我们新的MCC人源化小鼠模型，我们将能够首次检查肿瘤免疫小鼠， 对copanlisib和pembrolizumab的应答。重要的是，肿瘤 异质性是治疗失败和肿瘤进展关键决定因素。的最新进展 scRNA-seq使我们能够探索肿瘤和免疫细胞亚群对治疗的反应动力学。 为了实现我们的目标，我们将利用最先进的生物技术来全面分析 copanlisib和pembrolizumab治疗肿瘤和组织、细胞和分子水平的抗肿瘤免疫 程度.我们期望，成功完成拟议工作将带来以下进展：（1） 在MCC以及其他癌症中建立用于组合疗法的新治疗范例， 影响我们的退伍军人和他们的家庭成员，如黑色素瘤和高危头颈鳞状细胞癌 （2）鉴定介导药物应答的肿瘤和免疫细胞亚群，以及 对copanlisib和/或pembrolizumab治疗的敏感性/耐药性的生物标志物，这可能导致未来的 发现有效的治疗策略。从拟议研究中获得的知识将验证和 加快临床翻译，这将有助于退伍军人谁患有MCC和癌症，目前 免疫疗法是不够的。

Merkel cell carcinoma (MCC) is an aggressive skin cancer that has quadrupled in incidence with a dismal five- year survival rate of less than 18% in advanced diseases. MCC disproportionately and predominantly affects Caucasian males older than 65 who are well represented in our Veteran population, especially for those who are deployed to high UV index tropical and subtropical zones and are not well protected due to other survival priorities. Hence, MCC has a growing impact on the VA healthcare system. Currently, there is no Food and Drug Administration (FDA)-approved targeted therapy for MCC. Recently, immunotherapies such as pembrolizumab and avelumab have been FDA-approved for advanced MCC; nevertheless, a significant portion of patients still succumb to their diseases. Thus, there is an urgent clinical need for novel therapeutic strategies for patients who fail out of or are unsuitable for immunotherapy. Aberrant amplification and mutations of PI3K pathway have been detected in up to 80% of MCCs, making it an attractive therapeutic target. This is supported by our clinical success in treating a Stage IV MCC patient with the 1st FDA approved PI3K- inhibitor idelalisib, which elicited a complete clinical response. Furthermore, our preliminary studies demonstrate that copanlisib, the 2nd FDA approved PI3K inhibitor with activity predominantly against PI3K-α/ isoforms, exerts the most potent antitumor growth effects on MCC. Of relevance to this proposal, PI3K inhibition has been reported to enhance cancer immunotherapies. Thus, there is a strong rationale to develop new combinatorial immunotherapy with targeted therapies to boost therapeutic response and efficacy in MCC. Lack of syngeneic/genetically engineered animal models has hampered preclinical studies in MCC. Notably, in our preliminary studies we have successfully established a powerful, clinically relevant model system of MCC xenograft tumors in mice with competent human immune systems. We hypothesize that PI3K inhibition by copanlisib and PD-1 blockade by pembrolizumab will synergistically attenuate MCC tumor growth by inhibiting MCC cell proliferation and survival and enhancing tumor-infiltration of immune cells and their antitumor activities. Furthermore, we have optimized innovative single-cell RNA sequencing (scRNA-seq) methods to examine tumor heterogeneity and transcriptome profile in human MCC cells. Therefore, we are well positioned to pursue the following specific aims: (Aim 1) examine therapeutic efficacy and identify underlying mechanisms of copanlisib and pembrolizumab therapies on MCC xenograft tumor growth in humanized mice, and (Aim 2) identify cellular and molecular mechanisms of MCC tumor-immune interactions and antitumor immunity in response to copanlisib and pembrolizumab treatments. Using our novel MCC humanized mouse models, we will be able to examine, for the first time, tumor-immune response to copanlisib and pembrolizumab under competent human immune system. Importantly, tumor heterogeneity is a critical determinant of therapeutic failure and tumor progression. Recent advancements in scRNA-seq enable us to explore dynamics of tumor and immune cell subpopulations in response to treatments. To achieve our goals, we will utilize state-of-the-art biotechniques to comprehensively analyze the effects of copanlisib and pembrolizumab treatments on tumors and antitumor immunity at tissue, cellular, and molecular levels. We expect that successful completion of the proposed work will result in the following advances: (1) establishment of a novel treatment paradigm for combinatorial therapies in MCC, as well as other cancers that affect our Veterans and their family members such as melanoma and high-risk head and neck squamous cell carcinoma, (2) identification of tumor and immune cell subpopulations that mediate drug response, as well as biomarkers for sensitivity/resistance to copanlisib and/or pembrolizumab treatment, which can lead to future discovery of effective therapeutic strategies. Knowledge gained from the proposed studies will validate and accelerate clinical translation, which will help Veterans who suffer from MCC and cancers for which current immunotherapies are insufficient.